As is well known, as a type of flow path structure, a structure extending from a wall surface forming a flow path in a direction intersecting a main stream direction along a main stream of a fluid flowing through the flow path is known. For example, in a kind of exhaust diffuser of a gas turbine, while a bearing configured to support a rotor is installed in an exhaust casing and an annular space around the bearing becomes an exhaust flow path, a strut extending from an exhaust casing and configured to hold the bearing is disposed in the annular space (Patent Literature 1).